Based on your above post did Susan say 'NO, the alum lugs cannot be used'??
Did the manufacturer allude that the heater WITH the Al lug was a fully listed assembly. or were they saying the Al lug is 'listed'??
110.14 Electrical Connections. Because of different characteristics of dissimilar metals, devices such as pressure terminal or pressure splicing connectors and soldering lugs shall be identified for the material of the conductor and shall be properly installed and used. Conductors of dissimilar metals shall not be intermixed in a terminal or splicing connector where physical contact occurs between dissimilar conductors (such as copper and aluminum, copper and copper-clad aluminum, or aluminum and copper-clad aluminum), unless the device is identified for the purpose and conditions of use. Materials such as solder, fluxes, inhibitors, and compounds, where employed, shall be suitable for the use and shall be of a type that will not adversely affect the conductors, installation, or equipment.
Connectors and terminals for conductors more finely
stranded than Class B and Class C stranding as shown in
Chapter 9, Table 10, shall be identified for the specific
conductor class or classes.